The present invention relates to spacer structures which are located between a faceplate structure and a backplate structure in a flat panel display. The present invention also relates to methods for fabricating and installing such spacer structures.
Flat cathode ray tube (CRT) displays include displays which exhibit a large aspect ratio (e.g., 10:1 or greater) with respect to conventional deflected-beam CRT displays, and which display an image in response to electrons striking a light emissive material. The aspect ratio is defined as the diagonal length of the display surface to the display thickness. The electrons which strike the light emissive material can be generated by various devices, such as by field emitter cathodes or thermionic cathodes. As used herein, flat CRT displays are referred to as flat panel displays.
Conventional flat panel displays typically include a faceplate structure and a backplate structure which are joined by connecting walls around the periphery of the faceplate and backplate structures. The resulting enclosure is usually held at a vacuum pressure. To prevent collapse of the flat panel display under the atmospheric pressure, a plurality of spacers are typically located between the faceplate and backplate structures at a centrally located active region of the flat panel display.
The faceplate structure includes an insulating faceplate (typically glass) and a light-emitting structure formed on an interior surface of the insulating faceplate. The light emitting structure includes light emissive materials, or phosphors, which define the active region of the display. The backplate structure includes an insulating backplate and an electron emitting structure located on an interior surface of the backplate. The electron emitting structure includes a plurality of electron-emitting elements (e.g., field emitters) which are selectively excited to release electrons. The light emitting structure is held at a relatively high positive voltage (e.g., 200 V to 10 kV) with respect to the electron emitting structure. As a result, the electrons released by the electron-emitting elements are accelerated toward the phosphor of the light emitting structure, causing the phosphor to emit light which is seen by a viewer at the exterior surface of the faceplate (the xe2x80x9cviewing surfacexe2x80x9d).
FIG. 1 is a schematic representation of the viewing surface of a flat panel display 50. The faceplate structure of flat panel display 50 includes a light emitting structure which is arranged in a plurality of rows of light emitting elements (i.e., pixel rows), such as pixel rows 1-31. Flat panel display 50 typically includes hundreds of pixel rows, with each row typically including hundreds of pixels.
The electron emitting structure of flat panel display 50 is arranged in rows of electron emitting elements which correspond with the pixel rows 1-31 of the faceplate structure. Each row of electron emitting elements includes electron emitting elements which correspond to each of the pixels on the light emitting structure. The electron emitting elements are activated, thereby causing electrons to be transmitted to the corresponding pixels to create an image at the viewing surface of the flat panel display 50.
Spacer walls 41-43 are located between the faceplate structure and the backplate structure. Pixel rows 1-31 and spacers walls 41-43 are greatly enlarged in FIG. 1 for purposes of illustration. It is desirable for spacers 41-43 to extend horizontally across display 50 in parallel with pixel rows 1-31. Spacer wall 41 is illustrated as a properly positioned spacer wall. Spacer wall 41 is perfectly located between pixel rows 8 and 9, such that the spacer wall 41 does not obstruct any of the pixels in pixel rows 8 and 9. While spacer wall 41 illustrates the ideal positioning of a spacer wall, spacer walls 42 and 43 illustrate the positioning which results from conventional methods. Spacer wall 42, although straight, is not located perfectly in parallel with pixel rows 16 and 17. As a result, spacer wall 42 obstructs pixels near the ends of pixel rows 16 and 17. The obstructed pixels will not receive the intended electrons from the electron emitting structure, thereby resulting in degradation of the image viewed by the user. Spacer wall 43 exhibits a waviness which may be inherent in the material used to make the spacer wall 43. Spacer wall 43 therefore obstructs pixels throughout pixel rows 24 and 25, again degrading the image seen by the viewer. Spacer walls 41-43 can also be positioned in a non-perpendicular manner between the faceplate and backplate structures. Such a non-perpendicular positioning can result in the undesirable deflection of electrons. This electron deflection can also degrade the image seen by the viewer.
Consequently, it is desirable to have spacer walls which are precisely aligned within the flat panel display. However, the relatively small size of the spacer walls 41-43 makes it difficult to position these spacer walls 41-43 between the faceplate and backplate structures. Even if the spacer walls 41-43 are initially aligned properly, these spacer walls 41-43 can subsequently shift out of alignment during normal operation of the flat panel display. This shifting may occur as a result of heating or physical shock experienced by the flat panel display.
Spacer walls 41-43 can include face electrodes which are used to control the voltage distribution between the faceplate and backplate structures adjacent to the spacers 41-43. Predetermined external voltages are applied to the face electrodes to control this voltage distribution. It is often difficult to make an electrical connection between these face electrodes and either the faceplate structure and the backplate structure, such that the external voltages can be applied to the face electrodes.
It would therefore be desirable to have a spacer structure which is easy to locate between a faceplate structure and a backplate structure. It would also be desirable if this spacer would remain in precise alignment after assembly of the flat panel display, even in view of exposure to thermal cycling and physical shock. It would further be desirable if such a spacer facilitated easy connection of face electrodes to the faceplate and/or backplate structures.
Accordingly, the present invention provides a spacer structure which can be located between a faceplate structure and a backplate structure of a flat panel display. In one embodiment, the spacer structure includes a spacer wall having a first edge surface for contacting the faceplate structure and a second edge surface, opposite the first edge surface, for contacting the backplate structure. A first face surface extends between the first and second edge surfaces. A second face surface, which is located opposite the first face surface, extends between the first and second edge surfaces. The spacer wall further has a first end, and a second end located distal from the first end.
A first spacer foot is located on the first face surface at the first end of said spacer wall. The first spacer foot has a support surface which is co-planar with the first edge surface of the spacer wall. Similarly, a second spacer foot is located on the first face surface at the second end of said spacer wall. The second spacer foot has a support surface which is also co-planar with the first edge surface of the spacer wall. The first and second spacer feet advantageously enable the spacer wall to be supported in a free-standing position when the spacer wall is set on the first edge surface. To enhance the stability of the free-standing configuration of the spacer-wall, the support surfaces of the first and second spacer feet are located perpendicular to the first and second face surfaces of the spacer wall. When the spacer wall is positioned between a faceplate structure and a backplate structure, the support surfaces contact the faceplate (or backplate) structure, thereby holding the spacer wall in a perpendicular configuration between the faceplate and backplate structures.
In an alternative embodiment, third and fourth spacer feet can be attached to the spacer wall.- The third spacer foot is located on the second face surface at the first end of said spacer wall, and the fourth spacer foot is located on the second face surface at the second end of the spacer wall. Both the third and fourth spacer feet include support surfaces which are co-planar with the first edge surface of the spacer wall. These support surfaces are also perpendicular to the first and second face surfaces of the spacer wall. is The third and fourth spacer feet provide additional stability to the spacer wall. The spacer feet can be made from various materials, including, but not limited to ceramic, glass, and/or glass frit.
One method of fabricating a spacer wall having attached spacer feet includes the steps of: (1) firing a ceramic wafer having a first face surface, a first edge and a second edge opposite the first edge, (2) applying a first strip of glass frit on the first face surface adjacent to the first edge, (3) applying a second strip of glass frit on the first face surface adjacent to the second edge, (4) firing the first and second strips of glass frit, and (5) cutting the ceramic wafer and first and second strips of glass frit into spacer strips from the first edge to the second edge. In this method, the strips of glass frit form the first and second spacer feet.
In an alternative embodiment, glass bars can be positioned on the first and second strips of glass frit prior to the step of firing the first and second strips of glass frit. In this embodiment, the glass bars combine with the glass frit to form the first and second feet. In yet another embodiment, the glass frit can be replaced by strips of ceramic. In yet another embodiment, fired ceramic strips can be glued to glass canes, which are subsequently melted to join the fired ceramic strips to the ceramic wafer.
A method of installing a spacer wall in a flat panel display is also described. The method includes the steps of (1) forming one or more spacer feet at opposing ends of the spacer wall, (2) positioning the spacer wall on the faceplate structure (or the backplate structure) of the flat panel display, and (3) holding the ends of the spacer wall on the faceplate (or backplate) structure with an electrostatic force introduced by a plurality of electrodes formed in the faceplate (or backplate) structure. By applying an electrostatic force to the ends of the spacer wall, the spacer wall is advantageously held in place during assembly of the flat panel display. Once the electrostatic force has been applied, the ends of the spacer wall can be bonded to the faceplate (or backplate) structure. The electrostatic force can be eliminated after the flat panel display has been assembled. The spacer wall can be inserted into a groove in the faceplate (or backplate) structure during installation to further promote the alignment of the spacer wall.
Another method of installing the spacer wall includes the steps of (1) heating the spacer wall to a predetermined temperature to lengthen the spacer wall, (2) attaching the ends of the heated spacer wall to the faceplate structure or the backplate structure, wherein the faceplate (or backplate) structure is at a temperature which is lower than the temperature of the heated spacer wall, and (3) allowing the attached spacer wall to cool, such that the spacer wall cools and contracts. When the spacer wall contracts, the spacer wall is pulled straight, thereby eliminating any inherent waviness in the spacer wall.
Yet another method of installing the spacer wall includes the steps of (1) forming the spacer wall from a material having a first coefficient of thermal expansion (CTE), (2) forming the faceplate (or backplate) structure of a material having a second CTE, wherein the first CTE is greater than the second CTE, (3) heating the spacer wall and the faceplate (or backplate) structure to a temperature above room temperature, (4) attaching the ends of the spacer wall to the faceplate (or backplate) structure, and (5) allowing the spacer wall and the faceplate (or backplate) structure to cool and contract, wherein the spacer wall contracts more than the faceplate (or backplate) structure, thereby pulling the wall straight and eliminating any inherent waviness in the spacer wall.
Yet another method includes the steps of: (1) cooling the faceplate (or backplate) structure, thereby causing the faceplate (or backplate) structure to contract, (2) attaching the ends of the spacer wall to the faceplate (or backplate) structure, wherein the faceplate (or backplate) structure is at a temperature which is lower than the temperature of the spacer wall, and (3) allowing the faceplate (or backplate) structure to heat, such that the faceplate (or backplate) structure expands. When the faceplate (or backplate) structure expands, the spacer wall is pulled straight, thereby eliminating any inherent waviness in the spacer wall.
An alternative method of installing the spacer wall includes the steps of: (1) attaching spacer feet at opposing ends of the spacer wall, (2) mechanically lengthening the spacer wall by applying a force between the spacer feet, (3) attaching the ends of the spacer wall to the faceplate (or backplate) structure, and (4) removing the applied force between the spacer feet. The force can be applied by mechanical screws, a piezoelectric element, or a high thermo-expansion alloy. This method introduces longitudinal tension in the spacer wall which tends to remove any inherent waviness in the spacer wall.
Yet another method of installing the spacer wall includes the steps of (1) causing the faceplate (or backplate) structure to contract prior to bonding the spacer wall to the faceplate (or backplate) structure, (2) bonding the ends of the spacer wall to the faceplate (or backplate) structure, and (3) allowing the faceplate (or backplate) structure to expand after the spacer wall is bonded to the faceplate (or backplate) structure. The faceplate (or backplate) structure can be contracted by bending the faceplate (or backplate) structure into a concave configuration. This method also introduces a longitudinal tension in the spacer wall which tends to remove any inherent waviness in the spacer wall.
In yet another embodiment of the invention, the previously described spacer feet are replaced with spacer clips. Each spacer clip includes one or more spring-type elements which clamp the first and second face surfaces at an end of the spacer wall. The spacer clips can be made, for example, from an electrically conductive material, such as a metal, or from ceramic, glass, silicon, thermoplastic, or another dielectric material. Electrically conductive spacer clips can be used to provide an electrical connection to face electrodes located on the spacer wall. The spacer wall can be free-floating within the spacer clips, or affixed to the spacer clips in accordance with different embodiments of the invention. If the spacer wall is free-floating within the spacer clips, the spacer wall is free to expand and contract within the spacer clips, without distorting the spacer wall. If the spacer wall is affixed to the spacer clips, longitudinal tension can be introduced into the spacer wall by lengthening the spacer wall prior to affixing the spacer clips to the faceplate (or backplate) structure of the flat panel display, and then allowing the spacer wall to shorten after the spacer clips have been attached.
In yet another embodiment of the present invention, a spacer clip includes a ribbon of electrically conductive material which is bonded to the faceplate (or backplate) structure using a wirebonding process. The ribbon is bonded to form two adjacent loops which define a channel. During installation, the spacer wall is fitted into the channel.
The present invention will be more fully understood in view of the following detailed description taken together with the drawings.